A new efficient bis(phosphinite)-ruthenium(II) catalyst system for the asymmetric transfer hydrogenation of aromatic ketones

•A new chiral bis(phosphinite) ligand was synthesized.•The new catalyst system can readily be formed in situ.•The catalyst has been applied in the enantioselective hydrogenation of ketones.•Corresponding alcohols were obtained with high conversions and good ee’s.

Many chiral ligands bearing phosphorus donor atoms were developed and applied in the area of metal catalyzed asymmetric catalysis. A new chiral bis(phoshinite) ligand was successfully synthesized from optically active (1S,8S)-3,6-[N-(S)-α-phenylethyl]diaza-1,8-diphenoxymethyl-1,8-octanediol in high yield. A ruthenium(II) complex generated in situ from [Ru(η6-p-cymene)(μ-Cl)Cl]2, bis(phosphinite) ligand and KOH acts as an active catalyst for asymmetric transfer hydrogenation (ATH) of acetophenone derivatives in isopropyl alcohol (IPA) as both solvent and hydrogen source. The catalytic reaction proceeds cleanly to give enantiomerically enriched secondary alcohols up to 90% or 89% ee’s at 50 or 82 °C, respectively.

Graphical abstractWe report the use of chiral bis(phosphinite)-ruthenium(II) catalyst system as an efficient catalyst for asymmetric transfer hydrogenation of ketones. The new catalyst system can readily be formed in situ conditions in reaction media. This catalyst system gave the secondary alcohols up to 90% or 89% ee’s at 50 or 82 °C, respectively in the asymmetric transfer hydrogenation of acetophenone derivatives.Figure optionsDownload full-size imageDownload as PowerPoint slide